REED 00 C50SS, Manual, Page: 49 / 84

REED
00 MODEL:
C50SS
TRAILER CONCRETE PUMP
MAINT
PAGE 19
The S-tube shift hydraulic circuit is of the open center type, meaning that when the control
valves are in the
NEUTRAL position hydraulic non operational (unactuated), the internal
passages of the valves are open, free flow, allowing the hydraulic fluid to return to the tank.
With the engine running the hydraulic pump is operating, producing a flow of oil which, with
no control energized, will pass through the shift circuit on its way back to tank.
To meet the flow and pressure requirements of the shift circuit, one section of a tandem
pump is used. Note: a single pump is used if unit is not equipped with an agitator. The
TANDEM HYDRAULIC PUMP is of the gear pump design, having a fixed displacement
meaning it is designed to constantly produce the same displacement at pre-set maximum
engine RPM. The tandem gear pump is direct connected and driven through the gear box.
In addition to the hydraulic pump, the swing tube shift circuit consists of an unloader
manifold, an accumulator, a solenoid directional valve and two (2) hydraulic cylinders. The
following is offered to describe the function of each in the system.
SHIFT CIRCUIT MANIFOLD
The shift circuit is also equipped with a manifold block, which is located at the rear of the
hydraulic tank. It contains a relief cartridge, solenoid valve cartridge, check valve and a
differential pressure sensor. A solenoid operated directional valve is mounted on top of the
block and a S-tube selector control valve is located on front of the block. Each of these
components is designed to perform a particular function in the swing circuit as explained in
the following descriptions:
•
RELIEF CARTRIDGE - This cartridge is located on the top side of the manifold block
and is used to protect the system from excessive pressure and to limit the amount of
pressure being applied to the accumulator and is set at 2300 PSI (160 Bar)
•
UNLOADER VALVE - This cartridge is used to divert the pump flow from going to the
accumulator once its capacity has been reached, directing it back to tank. It becomes
operational when the relief cartridge setting has been reached.
•
SOLENOID VALVE CARTRIDGE – There are two (2) of these cartridges used in the
circuit. One, which may be referred to as a dump valve, is designed into the shift
circuit as a
SAFETY VALVE . Its purpose is to automatically relieve the pressure in the
accumulator through an orifice. The valve is controlled by the PUMP CYCLE switch
and the valve OPENS when the pump switch is OFF. This prevents the unintentional
shifting of the S-tube when the pump is not operating.
REVISION: